BUENOS AIRES, Argentina (AP) — Leading Tokyo's final pitch for the 2020 Olympics, Japan's prime minister assured the IOC on Saturday that the leak of radioactive water from the Fukushima nuclear plant is "under control" and will never affect Tokyo.

The Japanese city is competing against Madrid and Istanbul, with all three making their final presentations ahead of a vote later in the day by the International Olympic Committee.

Tokyo made its case as the "safe pair of hands," Madrid as the least expensive option, and Istanbul as the historic choice for a region yet to host the Olympics.

Tokyo has been considered a slight favorite but has been on the defensive in the final days of the campaign amid mounting concerns about the Fukushima leak.

"Some may have concerns about Fukushima," Prime Minister Shinzo Abe said in English. "Let me assure you the situation is under control. It has never done and will never do any damage to Tokyo."

Abe returned to the issue later when Norwegian IOC member Gerhard Heiberg asked for more assurances.

"It poses no problem whatsoever," Abe said in Japanese, adding that the contamination was limited to a small area and had been "completely blocked."

"There are no health related problems until now, nor will there be in the future," he said. "I make the statement to you in the most emphatic and unequivocal way."

Tokyo Electric Power Co., Fukushima's operator, has acknowledged that tons of radioactive water has been seeping into the Pacific from the plant for more than two years after the March 2011 earthquake and tsunami led to meltdowns at three of its reactors. Recent leaks from tanks storing radioactive water used to cool the reactors have added to fears that the amount of contaminated water is getting out of hand.

With major risks surrounding each bid, the final presentations could help decide a tight race. Abe and Prime Ministers Recep Tayyip Erdogan of Turkey and Mariano Rajoy of Spain all flew to Buenos Aires straight from the G20 summit in St. Petersburg, Russia.

All three are repeat bidders: Istanbul for a fifth time overall, Madrid for a third straight and Tokyo a second in a row. Picking the city with the least risks shapes up as the challenge for the IOC.

IOC elections are extremely unpredictable as members vote by secret ballot and take different personal reasons into account. Some members are still undecided and will be waiting for the final presentations before making up their mind.

With two IOC members absent, 95 will be eligible to vote in the first round. With a majority required for victory, the process is likely to go two rounds. The city with the fewest votes is eliminated after the first round, setting up a final head-to-head ballot. Outgoing IOC President Jacques Rogge will open a sealed envelope to announce the winner.

Tokyo, which hosted the 1964 Olympics, continued to portray itself as the safe choice at a time of global political and economic uncertainty.

"Tokyo can be trusted to be the safe pair of hands and much more," bid leader and IOC member Tsunekazu Takeda said. "Our case today is simple. Vote for Tokyo and you vote for guaranteed delivery. ... Tokyo is the right partner at the right time."

Tokyo's delegation also included Japan's Princess Takamado.

"This may be the first time a member our family has addressed you, but the imperial family of Japan has always been active in sports," she said.

Madrid, which has picked up momentum in recent weeks, contended that its bid makes the most economic sense, a project that can help Spain recover from severe recession and 27 percent unemployment rate. Madrid says 80 percent of its venues are ready and only $1.9 billion is needed for construction, a fraction of the other two bids.

"Madrid has perhaps the most reasonable and responsible financial foundation in recent Olympic history," Rajoy said. "We can host the Olympics in 2020 with no risk to the Olympic movement."

Crown Prince Felipe, a former Olympic sailor and Spain's flag-bearer at the 1992 Barcelona Games, said holding the games during difficult economic times is an "opportunity" for the country. He called the bid "both affordable and a responsible model for the future."

"We aren't talking about dreams, but realities," bid leader Alejandro Blanco said. "We're not talking about concepts. We aren't throwing away money, nor are we building castles in the sky."

"If you choose Madrid today," he said, "I know that you will find no safer home for the 2020 Games, and no greater partner for next seven years than the people of Spain."

After the presentation, Heiberg asked Madrid about Spain's position on doping, which has been perceived as lax.

"Spain is at the same level as all other countries fighting doping," Blanco said. "We've had a problem in the past, but we have prosecuted the athletes as well as those who harmed the health of the athletes."

Blanco also said Spain had adopted a new anti-doping law.

"Please have no doubt," he said. "We are a reliable partner. We believe in clean sports, we believe in athletes. You will always have Spain at your side."

Istanbul, making its fifth overall bid, was up first. The Turkish delegation pressed its case to take the Olympics for the first time to a predominantly Muslim country, to a city linking the continents of Europe and Asia.

With the civil war in neighboring Syria posing a major issue for the Istanbul bid, Erdogan said taking the games to Turkey "will send a very meaningful and strong message, not only to the world, but to our broader region."

"At this critical moment, we would like to send a strong message of peace to the whole world from Istanbul," Erdogan said.

After the formal presentation, IOC member Prince Albert of Monaco asked what hosting the games in Turkey would mean to the wider region.

"We believe that hosting the Olympics in Istanbul will give this signal, this spirit of friendship and sharing and peace," Erdogan said. "And our country is a place where there is a lot of unity and diversity, and that is the idea that we can share on a broader scale with the Olympics Games being hosted in Turkey."

Istanbul's bid has also been hit hard by the anti-government protests in June and a slew of doping scandals among Turkish athletes.

Turkish IOC member Ugur Erdener promised that Turkey "will continue to enforce our zero-tolerance policy on doping." Sports Minister Suat Kilic said Turkey would use criminal laws to prosecute anyone involved in promoting the use of banned substances.